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The color of aquatic animals plays an important role in consumer acceptability and perceived quality. In a previous study, a red claw crayfish Cherax quadricarinatus strain with steady and hereditary shell color of blue was selected. To evaluate the potential value of this strain in crayfish culture, the growth performance, carotenoid content, and temperature tolerance of two crayfish strains (shell color; blue and blue-green) were conducted. After the 56-day rearing period, blue crayfish showed higher feed intake and growth rate, but lower survival than blue-green crayfish. Astaxanthin was the main pigment observed in the carapace of both strains, and the content of astaxanthin in blue crayfish was 18.62 mg/kg of wet weight, which was significantly lower than that of astaxanthin in blue-green crayfish (83.23 mg/kg of wet weight). The 7-day survival of two crayfish strains less than 34°C was 100%, and blue-green crayfish showed stronger tolerance to high water temperature exposure (35°C–38°C) than blue crayfish. Furthermore, after high temperature stress, lower activities of superoxide dismutase and catalase, and higher malondialdehyde in the hepatopancreases of blue crayfish were observed than those in blue-green crayfish. This study provides important information for future breeding programs for the red claw crayfish.

The effects of high hydrostatic pressure (HHP) processing at 200 MPa, 400 MPa, and 600 MPa on the proximate composition, inactivation of bacteria, and color of the red claw crayfish Cherax quadricarinatus were evaluated. High hydrostatic pressure processing resulted in complete shelling and a significant decrease in the moisture content (P < 0.05), whereas no significant differences were observed in the content of ash, crude protein, and crude lipid, except for the crude lipid content between 200 MPa and 600 MPa groups (P < 0.05). After pressurization, the Escherichia coli, Vibrio vulnificus, and Vibrio parahaemolyticus counts decreased significantly with the increase of pressure, even to an undetected level for V. vulnificus and V. parahaemolyticus at 400 and 600 MPa (P < 0.05), respectively. During 30-d storage at 4°C and –20°C, the counts of these three bacterial species increased significantly with increased storage time and temperature. After HHP processing, a* value changed substantially, whereas L* and b* values had little change for meat. The total color difference (ΔE*) suggested that the HHP-treated red claw crayfish exhibited very distinctive or substantial differences compared with fresh individuals.

Relationships between shell morphological traits and byssus dimensions in adult winged pearl oysters Pteria penguin are described to include a more detailed description of byssus growth in juveniles under typical culture conditions. Byssus growth, byssus diameter (BD) relations between the byssus and shell traits [shell height; total wet weight (TW)], byssus occurrence, and the size distributions in samples collected monthly or bimonthly over a 1-y duration were recorded. Pearl oysters exhibited continuous shell growth and weight increase over the experimental period, but byssal measurements exhibited a different pattern. The increase in BD decreased as oysters aged and no further increase was observed after day 267. Moreover, BD/TW ratio exhibited a steadily diminishing trend as P. penguin aged. The relationships between the BD and the shell traits in 68-day-old oysters proved to be insignificant, probably because the oysters were neither heavy nor large enough to exhibit the relationships, but later, when oysters increased in size and weight, the relationships became significant. Byssus diameter was determined to be slightly more closely related to the weight of the animal than the size of the shell, and oysters at day 183 exhibited comparatively higher r2 values than oysters at day 366 of cultivation. The occurrence of oysters without byssus decreased gradually during cultivation from 30% initially to 0 after a year of cultivation.

The relationships of the shell morphological traits, including the byssus dimensions, were recorded and analyzed in sample groups of 18- and 30-mo-old cultured winged pearl oysters, Pteria penguin. All relationships among shell dimensional traits with respect to shell height (SH) in the 18- and 30-mo-old oysters were observed to be positive and significant (P < 0.05). Although allometric growth was observed in both groups, the r2 values in the relationship between SH and total wet weight (TW) were higher in old oysters than in young ones. These findings indicate that weight in young oysters is heterogeneous. Moreover, the TW—SH ratio showed a clearer tendency to increase relative to exterior dimensions in old oysters. The r2 values in the correlation between SH and maximum dorso-ventral length were the highest in both oyster groups; hence, this dimension is a reliable predictor of SH. On the other hand, the relationships between SH and either hinge length or shell thickness were slightly weak in both age groups. Oysters with no byssus were found only in the younger group. It is possible that older oysters are less susceptible to factors that induce byssus shedding. In young oysters, the length and diameter of the byssus was closely related to the weight of the animal rather than the size of the shell. But, as individuals continued gaining weight, no augmentation in the byssus organ diameter was measured, suggesting a threshold for the byssus diameter in heavier oysters. Because it is possible that byssus size may influence the quality of pearls formed in the oyster due to the proximity of the pearl sac to the byssus root, it is important to consider the weight of the oysters selected or cultivated for pearl production, as this may indirectly affect the quality of the finished pearl product.

This study determined the biochemical composition of the adductor muscle and mantle of two species of the giant clams Tridacna crocea and Tridacna squamosa harvested from the lagoon of South China Sea. Moisture, crude protein, crude lipid, and ash contents of the giant clams (% wet weight) ranged 77.01%–81.47%, 10.90%–15.59%, 0.39%–1.02%, and 2.25%–3.23%, respectively, with some significant differences between species and tissues (P < 0.05). The total amino acid and essential amino acid contents of the adductor muscle were 62.20–61.07 g/100 g and 24.89–24.80 g/100 g, respectively, significantly higher than those in the mantle (52.80–55.98 g/100 g and 17.85–19.73 g/100 g, respectively) (P < 0.05). Total saturated fatty acids (SFA) were found to be higher than total monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA), accounting for 41.53%–55.40% for SFA, 25.83%–27.31% for MUFA, and 18.63%–31.25% for PUFA. There was no difference between the MUFA profiles of T. crocea and T. squamosa, whereas the PUFA profiles in T. squamosa were significantly higher than those in T. crocea (P < 0.05). The ratios of total n-3 PUFA to n-6 PUFA were the highest in the mantle of T. squamosa (6.60), followed by the mantle of T. crocea (2.54), and finally, the adductor muscle of T. crocea (1.82) and T. squamosa (1.09). Therefore, these two giant clam species, T. crocea and T. squamosa, are excellent sources of several nutrients that could be beneficial for the health of consumers.

The present study describes the effects of various wavelengths of light on locomotion and byssal reattachment activities in the pearl oyster Pteria penguin, the most widespread cultured winged oyster for the production of valuable mabe pearls. Responses of pearl oysters to light have not yet been carefully observed and documented, despite the fact that light is known to influence the positioning of animals within the water column subject to local environmental conditions. To appropriately assess oyster movements and subsequent byssal reattachment, juveniles were filmed during unnatural light–dark cycles, alternating light and darkness every 6 h. Another experiment, to observe reactions to different light colors, was carried out by subjecting juveniles to either red or blue light during a continuous observation period of 24 h. Byssal reattachment for each juvenile was recorded at the end of each observation period. Light, independent of its color, strongly inhibited both locomotion and byssal reattachment activities in juveniles. Moreover, locomotion was observed to be unrelated to the shell size, but it is suggested that a large byssus may be responsible for inhibiting movement by preventing complete extension of the foot. High byssal reattachment rates to substrata under darkness in oyster juveniles is an important factor to take in consideration after detachment events during cleaning or when transplanting seeds to farm grounds.

Complete mitochondrial genomes of Pinctada fucata martensii and Pteria penguin were sequenced. The P. fucata martensii mitogenome was 31,435 bp long, which made it the longest genome so far published in the Pinctada and Pteria. The mitochondrial genome of P. penguin lacked three transfer RNA (tRNA) genes and had one duplicated tRNA gene; this mitogenome has the fewest tRNA of any mitogenome so far available in the Pinctada and Pteria. Both mitogenomes were strongly skewed away from C in favor of G and away from A in favor of T. The mitogenomic gene order in these two species was incongruent with mitogenomic gene orders for other species of Pteriomorphia, and Pteria penguin was placed as sister to all other Pinctada species. This study provided insights into the evolutionary relationships among Pteriidae species.